Odd triplet superconductivity in a superconductor/ferromagnet structure with a spiral magnetic structure

TL;DR

This paper investigates how a spiral magnetic structure in a superconductor/ferromagnet system influences the long-range triplet component, revealing a transition from exponential decay to oscillatory behavior depending on the cone angle and ferromagnet strength.

Contribution

It provides a detailed analysis of the LRTC behavior in S/F structures with spiral magnetism, including the effects of cone angle and ferromagnet strength on decay and oscillations.

Findings

LRTC decays exponentially at small cone angles

Oscillations in LRTC appear when cone angle exceeds a threshold

Josephson current depends on ferromagnet thickness and magnetic structure

Abstract

We analyze a superconductor-ferromagnet (S/F) system with a spiral magnetic structure in the ferromagnet F for a weak and strong exchange field. The long-range triplet component (LRTC) penetrating into the ferromagnet over a long distance is calculated for both cases. In the dirty limit (or weak ferromagnetism) we study the LRTC for conical ferromagnets. Its spatial dependence undergoes a qualitative change as a function of the cone angle \theta. At small angles the LRTC decays in the ferromagnet exponentially in a monotonic way. If the angle \theta exceeds a certain value, the exponential decay of the LRTC is accompanied by oscillations with a period that depends on \theta. This oscillatory behaviour leads to a similar dependence of the Josephson critical current in SFS junctions on the thickness of the F layer. In the case of a strong ferromagnet the LRTC decays over the length which is determined by the wave vector of the magnetic spiral and by the exchange field.